Removing all whitespace lines from a multi-line string efficiently

Question

If you want to remove lines containing any whitespace (tabs, spaces), try:

string fix = Regex.Replace(original, @"^\s*$\n", string.Empty, RegexOptions.Multiline);

Edit (for @Will): The simplest solution to trim trailing newlines would be to use TrimEnd on the resulting string, e.g.:

string fix =
    Regex.Replace(original, @"^\s*$\n", string.Empty, RegexOptions.Multiline)
         .TrimEnd();